1. Field of Invention
The present invention relates to a universal joint, particularly relates to a universal joint suitable for being used for a drive system operated with a high load such as a rolling mill or the like.
2. Background Art
A mechanism of driving, for example, a roll of a rolling mill is provided with a universal joint between a driving motor and the roll. There is known a universal joint of this kind referred to as a block type as shown in a disassembled perspective view of an essential portion thereof in FIG. 3, a sectional view of a trunnion portion orthogonal to an axis thereof in FIG. 4, and a sectional view taken along a line A-A thereof in FIG. 5, respectively (refer to, for example, Patent Reference 1).
The universal joint of the block type adopts a structure in which respective trunnions 11 of a joint cross 1 are supported by bearing cups 3 through rollers 2, and the respective bearing cups 3 are fixed to yokes 4 by bolts 5, respectively. The bearing cup 3 is integrally formed with a key portion 31 projected to a side of the yoke 4 at a joint surface thereof to the yoke 4, and by fitting the key portion 31 to a key way 41 formed at the yoke 4, a torque is transmitted thereby in cooperation with the bolt 5. That is, a rotational power of the yoke 4 on one side is transmitted to the bearing cup 3 through the trunnion 11 of the joint cross 1 as a load at a position indicated by an arrow mark in FIG. 4 and is transmitted to the yoke 4 on other side by an axial force of the bolt 5 and a surface pressure between the key portion 31 and the key way 41. As a material of the bearing cup 3, carburized and quenched steel of, for example, SNCM or the like is used in consideration of a shock resistant load performance as a bearing ring of the bearing.
The universal joint of the block type achieves an advantage that a number of pieces of parts is small and the bearing cup is not creeped in view of a structure thereof in comparison with other type of a universal joint such as around type in which a bearing cup in a cylindrical shape is fixed to a yoke by a member referred to as a bearing holder of a separate member.
Patent Reference: JP-A-2002-181069